virtualbox.org

With:
Windows 7 Po SP1 64 bit
VirtualBox 5.0.2
Intel i7-2640M

I noticed that VB gives the "VT-x is being used by another hypervisor.(VERR_VMX_IN_VMX_ROOT_MODE)" error if VirtualPC is running at the same time.
But if VMware Player is running (also in VT-x mode), VirtualBox does not complain and run its VMs just fine.
(that is VMware + VB, but not VPC)

The guests are 64 bit, except the VPC guest (VPC does not support 64 bit guests).

Is VMware's use of VT-x not a problem for VB? Or is it not detected? Something else?

Regards,
David

Most hypervisors play well together with the exception of one. MS does not want you to play with anything else.

Just an information: VMware Player works fine in VT mode while VPC is running (according to its settings and log:
vcpu-0| I120: Intel VT enabled.
vcpu-1| I120: Intel VT enabled.
)

Then that is what you should use.